1. Field of the Invention
The present invention relates to a mobile terminal and a control method thereof. More specifically, the present invention relates to a mobile terminal having hardware keys and a control method thereof.
2. Description of the Related Art
One example of a related art of a mobile terminal of such a kind is disclosed in a Japanese Patent Application Laying-Open No. 2006-262533 [H04M 1/73, H04M 1/00] (document 1) laid-open on Sep. 28, 2006. In the mobile phone of this document 1, a key operating portion need not be operated during reception of information and execution of a karaoke function, and therefore, although a liquid crystal panel and a key operating portion are illuminated for a predetermined period from the start of the information reception and the karaoke function, but after a lapse of the predetermined period, lighting of the key operating portion is suspended while lighting of the liquid crystal panel is maintained. Furthermore, in the mobile phone of the document 1, in a sending operation of electronic mail, when a “character/numeric input mode” is not executed, lighting of a numeric keypad (character/numeric input key) is suspended. Thus, in the mobile phone of the document 1, electric power consumption by the lighting is reduced.
Furthermore, another example of the related art of the mobile terminal of such the kind is disclosed in a Japanese Patent Application Laying-Open No. 2009-188619 [H04M 1/00, H04M 1/725, G06F 3/02] (document 2) laid-open on Aug. 20, 2009. The mobile terminal apparatus of the document 2 make a liquid crystal and a key backlight light up when detecting the start of opening a sliding portion of cases, and displays a standby screen on a displayer when detecting the open position of the sliding portion at the latest. Thus, a waiting time from when the user opens the sliding portion to when he or she operates the mobile terminal apparatus is shortened.
Additionally, a still another example of the related art of performing a key backlight control of turning off the backlight for a fixed period of time measured by the time counter in response to detection of depression of a key, and reducing a consumption current during a key operation is disclosed in a WO 2008/038381 [G06F 3/02, G06F 1/28, H04M 1/73, H04M 1/02, H04M 1/22] (document 3) laid-open on Apr. 3, 2008.
However, in the document 1, after lighting of the liquid crystal panel and the key operating portion is suspended, if a touch operation to a touch sensor or a key operation to a key operating portion is performed, lighting both of the key operating portion and the liquid crystal panel is started. Thus, when lighting the key operating portion is started in response to a touch operation, if no operation is performed on the key operating portion thereafter, waste of electric power consumption due to lighting of the key operating portion occurs.
Also, in the document 2, when the sliding portion of the mobile terminal apparatus starts to be opened, the key backlight is lit up, and therefore, a waste of electric power consumption from the start of the light-up to the key operation occurs. Furthermore, after the sliding portion of the case of the mobile terminal apparatus is opened, if no operation is performed as well, a waste of electric power consumption due to lighting the key backlight similarly occurs.
In addition, in the document 3, a consumption current during the key operation can be reduced, but even if the technique of the document 3 is adopted, it is impossible to solve the problem of the document 1 and the document 2.